This introduces winbits.[ch] in the engine, containing layer-independent code migrated from winlayer, including nedmalloc, ebacktrace1, OS version detection, and high-resolution profiling timers.
sdlayer has been expanded to include the code from winbits under _WIN32.
All uses of RENDERTYPEWIN in the source have been examined and changed to _WIN32 (or removed) where the block in question is layer-independent.
git-svn-id: https://svn.eduke32.com/eduke32@3221 1a8010ca-5511-0410-912e-c29ae57300e0
